With the development of nanotechnology, a large number of metal nanoparticles are being developed and produced with new formulations and surface properties to meet novel demands. For example, as an important transition metal, nickel nanoparticles (Nano-Ni) have wide ranging applications in the fields of batteries, electrical conductors, permanent magnets, magnetic fluids, magnetic recording media, solar energy absorption, fuel cell electrodes, and catalysts. In addition, due to structural and inherent chemical and physical properties, nickel alloy nanomaterials have received special interest in biomedical applications. As the use of nanomaterials continues to grow, the risk of environmental contamination by nanoparticles is increases. The term 'Nanotoxicology' has been used to put forward the concept that nanoparticles might represent a unique class of particulate toxins that differ from conventional pathogenic particles. In this proposal, we selected Nano-Ni as a model metal nanoparticles because of its wide industrial interest and biological and medical applications. Based on our preliminary data, we hypothesize that Nano-Ni will activate monocytes/macrophages, altering the expression and activity of matrix metalloproteinases (MMPs) through hypoxia inducible factor 1a (HIF-1a) and microRNA miR-21. It is possible that structurally- tailored Ni-containing nanoparticles such as nickel alloy nanoparticles, could have fewer or even no effects. This would be very important to know. This project will use both in vitro and in vivo systems to address the following objectives. (1). Determine the alteration of MMPs and TIMPs expression and activity in monocytes/macrophages exposed to Nano-Ni or nickel alloy nanoparticles in vitro and in vivo. We will examine whether exposure to Nano-Ni will alter MMP-2, MMP-9, TIMP-1 and TIMP-2 production in both U937 cells (human leukemic monocyte lymphoma cell line) and monocytes isolated from mice, by using quantitative real-time PCR, gelatin zymography or reverse zymography assay in vitro. We will also determine the alteration of MMPs and TIMPs expression and activity in monocytes isolated from Nano-Ni-exposed mice. We will investigate whether nickel alloy nanoparticles, Nano-Ni core and silica or carbon shell, and silica or carbon supported Nano-Ni will reduce the Nano-Ni-induced activation of MMPs and toxic effect in vitro and in vivo settings. (2). Examine HIF-1a accumulation in monocytes/macrophages with exposure to Nano-Ni and the role of HIF-1a on the Nano-Ni-induced alteration of MMPs expression and activity. We will measure the HIF-1a level in U937 cells with exposure to Nano-Ni. To investigate the role of HIF-1a in Nano-Ni- induced MMPs expression and activity, we will employ the following strategies: (1) use of HIF-1a inhibitors such as heat-shock protein 90 (Hsp90); (2) use of HIF-1a-specific siRNA to knock-down HIF-1a expression; and (3) use of HIF-1a knock-out cells. (3). Investigate whether Nano-Ni-induced alteration of MMPs expression and activity through up-regulation of microRNA miR-21 by activation of HIF-1a. We will first identify whether exposure to Nano-Ni will cause up-regulation of miR-21 by quantitative real-time PCR. We will then investigate whether miR-21 modulates MMPs expression and activity by activation HIF-1a by using: (1) pre-miR-21 transfection to increase the abundance of miR-21 in the cells; (2) anti-miR-21 transfection to lower the level of miR-21 in the cells; and (3) use HIF decoy to block the activity of endogenous HIF transcription factor in the cells.